Polycarbonate resins have been used as a material for molded products in various industrial fields because of its excellent mechanical characteristics, thermal characteristics and electrical characteristics. Recently, the polycarbonate resin has often been used in a field of a functional product requiring optical characteristics of the polycarbonate resin as well as the above characteristics. In accordance with such an expansion in application, the polycarbonate resin has been demanded to have a variety of performance.
The functional product is exemplified by an electrophotographic photoreceptor in which the polycarbonate resins are used as a binder resin for functional materials such as a charge generating material and a charge transporting material.
The electrophotographic photoreceptor has been demanded to have a predetermined sensitivity, electrical characteristics and optical characteristics in accordance with electrical photography process to be applied. A surface of a photosensitive layer of the electrophotographic photoreceptor is repeatedly subjected to operations such as corona electrification, toner development, transfer onto paper, cleaning and the like. Electrical and mechanical external-forces are applied on the surface of the photosensitive layer every time such operations are performed. Accordingly, the photosensitive layer provided on the surface of the electrophotographic photoreceptor is required to have durability against these external forces in order to maintain electrophotography image quality for a long period of time.
Moreover, since the electrophotographic photoreceptor is typically manufactured by dissolving a functional material and a binder resin in an organic solvent and film-casting the obtained solvent on a conductive substrate and the like, the electrophotographic photoreceptor is required to have solubility in the organic solvent and stability of the obtained solvent.
Traditionally, a polycarbonate resin using, for instance, 2,2-bis(4-hydroxyphenyl)propane (bisphenol A) and 1,1-bis(4-hydroxyphenyl)cyclohexane (bisphenol Z) as an ingredient have been used as a binder resin for an electrophotographic photoreceptor. However, such a polycarbonate resin is insufficient to satisfy durability such as wear resistance. In view of the above, various techniques have been used in response to such demands. A copolymerized polycarbonate has been known as one of effective techniques (see, for instance, Patent Literatures 1 to 3).
A resin disclosed in Patent Literature 1 includes a polycarbonate copolymer manufactured by copolymerizing a component having a biphenol skeleton that contributes to wear resistance with a component having a bisphenol Z skeleton that contributes to solubility. This polycarbonate copolymer is proved to have a wear resistance superior to that of a bisphenol-Z polycarbonate homopolymer.
Patent Literature 2 discloses an alternating copolymerized polycarbonate of bisphenol A and biphenol. The alternating copolymerized polycarbonate, in which a ratio of biphenol per copolymer is increased, is produced from an oligomer of a small number of repeating units as a starting material. A copolymerization ratio of biphenol contained in the alternating copolymer is 50 mol %.
Patent Literature 3 discloses technique for manufacturing a bischloroformate compound by reacting, for instance, bisphenol A and bisphenol Z with phosgene.